The present invention relates to an ultrasonic motor having an electrical connecting construction for a piezoelectric element for friction-driving a moving body by a vibration wave utilizing an expansion/contraction movement of the piezoelectric element.
An electrical connecting construction for a piezoelectric element in a conventional ultrasonic motor, as shown in FIG. 7, is one in which a plurality of lead wires 7 are connected to a plurality of electrodes 2 formed on a piezoelectric element 1. Soldering is a representative method of connecting wires 7 to electrodes 2. That is, the lead wires 7 are joined to the electrodes 2 formed on a surface of the piezoelectric element 1 by solder joints 8.
However, in the construction of the conventional ultrasonic motor, since the plurality of lead wires 7 are connected to the electrodes 2 formed on the surface of the piezoelectric element 1 one by one, considerable time is required to connect the lead wires, which results in an increase in production cost.
In addition, in a case where the ultrasonic motor is miniaturized, a degradation in operating characteristics and the increase in cost become substantial due to the manner of connecting the plurality of lead wires 7.
Also, the strength of the connections between the lead wires 7 and the electrodes 2 is low, and this creates problems with respect to reliability.
Furthermore, since the lead wires 7 are joined the electrodes 2 one by one by soldering and the like, the time period during which the element receives heat becomes long and this has a harmful influence on the polarized state of the piezoelectric element 1.
FIG. 8 is a sectional view of an ultrasonic motor according to the prior art. Piezoelectric element 1 is joined to a vibrating body 106 and a plurality of electrodes 2 are pattern-formed on piezoelectric element 1. The vibrating body 106 is guided by a center shaft 102 and is supported fixedly on the center shaft 102 in the vicinity of the center thereof so as to be assembled with the fixed bed 101 on which the lead board 5 is arranged. A moving body 104 is guided by a center shaft 102 for rotation relative to center shaft 102 and the body 104 is capable of rotating by contacting a vibrating body 106 with a predetermined pressure produced by a pressing member 105 that bears against body 104 at a point along the axis of shaft 102. An elastic body such as a coil, a spring, a plate spring, etc., may be employed as the pressing member 105, and several such bodies may be used jointly.